1. Field of the Invention
The present invention relates to a light emitting device using a light emitting element which generates fluorescence or phosphorescence by applying an electric field to the element provided with a layer containing an organic compound (hereinafter referred to as an “organic compound layer”) between a pair of electrodes, and a manufacturing method of the light emitting device. Note that the light emitting device refers to an image display device, a light emitting device, and a light source (including a lighting system).
2. Description of the Related Art
A light emitting element using an organic compound as a luminous body, which has features such as thinness, lightness, high-speed response, and DC drive at low voltage, is expected to be applied to a next-generation flat panel display. In particular, a display device in which light emitting elements are arranged in matrix is considered to have an advantage in a wide viewing angle and excellent visibility over a conventional liquid crystal display device.
It is said that as for a light emitting mechanism of the light emitting element, light is emitted by applying a voltage between a pair of electrodes where an organic compound layer is interposed, so that electrons injected from a cathode and holes injected from an anode are recombined with each other at a light emitting center of the organic compound layer to form molecular excitons and the molecular excitons release energy when returning to a ground state. Singlet excitation and triplet excitation are known as excited states, and it is thought that light emission can be achieved through either of the excited states.
For the light emitting device in which light emitting elements are arranged in matrix, a driving method such as passive matrix driving (simple matrix type) or active matrix driving (active matrix type) can be used. However, when the pixel density is increased, the active matrix type where each pixel (or each dot) is provided with a switch is thought to be advantageous because it can be driven at lower voltage.
In the case of manufacturing an active matrix light emitting device, a TFT is formed over a substrate having an insulating surface as a switching element, and EL elements each of which uses a pixel electrode electrically connected to the TFT as an anode or a cathode are arranged in matrix.
In the case of manufacturing an active matrix light emitting device or a passive matrix light emitting device, a partition for insulating adjacent pixels from each other is formed at an end portion of the pixel electrode.
The applicant of the present invention has proposed partitions disclosed in References 1 and 2 (Reference 1: Japanese Patent Laid-Open No. 2002-164181, and Reference 2: Japanese Patent Laid-Open No. 2004-127933).
In a display device provided with an electroluminescent (hereinafter also referred to as EL) element, a color light emitting element which emits color light is used in order to perform full-color display. It is one of important factors to form a light emitting material of each color over an electrode in a minute pattern in order to form a color light emitting element.
For the above purpose, a method for forming into a minute pattern using a mask is generally used when forming a material using an evaporation method or the like.
However, as a result of miniaturization of a pixel region associated with an improvement in definition and an increase in a substrate size associated with an increase in area, defects due to precision, bending, and the like of a mask used at the time of evaporation have become issues.